US4488130A - Microwave integrated circuit, bandpass filter - Google Patents

Microwave integrated circuit, bandpass filter Download PDF

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Publication number
US4488130A
US4488130A US06/469,498 US46949883A US4488130A US 4488130 A US4488130 A US 4488130A US 46949883 A US46949883 A US 46949883A US 4488130 A US4488130 A US 4488130A
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Prior art keywords
resonators
transmission line
integrated circuit
coupling means
microwave integrated
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US06/469,498
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Frederick A. Young
Robert J. Ahulii
Roy K. Rikimaru
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DirecTV Group Inc
Raytheon Co
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Hughes Aircraft Co
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Assigned to HUGHES AIRCRAFT COMPANY, A CORP. OF DEL. reassignment HUGHES AIRCRAFT COMPANY, A CORP. OF DEL. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: AHULII, ROBERT J., RIKIMARU, ROY K., YOUNG, FREDERICK A.
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Assigned to HUGHES ELECTRONICS CORPORATION reassignment HUGHES ELECTRONICS CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HE HOLDINGS INC., HUGHES ELECTRONICS, FORMERLY KNOWN AS HUGHES AIRCRAFT COMPANY
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters
    • H01P1/20327—Electromagnetic interstage coupling
    • H01P1/20354—Non-comb or non-interdigital filters
    • H01P1/20381—Special shape resonators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/205—Comb or interdigital filters; Cascaded coaxial cavities

Definitions

  • the present invention relates to filters and, more particularly, to a microwave integrated circuit including a bandpass filter.
  • microwave integrated circuit filters are used to select utilized frequencies and to reject unwanted frequencies which can result in noise.
  • One design goal of such filters is to obtain sharp out-of-band rejection.
  • One commonly employed microwave wave circuit (MIC) bandpass filter is the combline filter.
  • This filter includes a longitudinally extending transmission line section and plural, usually four, spaced resonators extending from and orthogonal to the transmission line.
  • the four resonator combline filter represents an useful compromise between economy and effectiveness. More effective filtering can be achieved using more than four resonators, but the added cost and complexity of manufacture tend to outweigh the gain in effectiveness. Furthermore, the added bulk of the larger filters is a significant disadvantage in space and other applications where size and weight are at a premium. What is needed is a compact and economical filter which provides greater filtering effectiveness than the available four-section filter.
  • the present invention provides an improved filter for electromagnetic waves.
  • the filter includes a transmission line andl plural resonators spaced from one another and extending from the transmission line. Means are provided electromagnetically coupling nonadjacent resonators.
  • the performance of a standard four-section combline filter in a microwave integrated circuit is enhanced by providing means for coupling the first and fourth resonators.
  • the coupling means may be a gold ribbon, or a ribbon of other conductive material, or an alternative structure.
  • the coupling means may be capacitively coupled to one resonator and inductively coupled to the other. For different applications, both couplings may be inductive, or both may be capacitive.
  • FIG. 1 is a bandpass filter in accordance with the present invention.
  • FIG. 2 is a graph depicting the comparative performances of a coupled filter in accordance with the present invention with an uncoupled filter in accordance with the prior art.
  • a filter 10 in accordance with the present invention includes a multitude of spaced resonators 12, 14, 16 and 18, as shown in FIG. 1.
  • the resonators extend from a common transmission line 20.
  • the comblike structure results in the common appellation "combline" filter.
  • the filter 10 is coupled to an input line 22 by an input coupling means 24 and to an output line 26 by an output coupling means 28.
  • a conductive ribbon 30 or other means couples nonadjacent resonators 12 and 18.
  • a microwave integrated circuit 11 includes a substrate 38, preferably of alumina, and a four-section combline filter 10.
  • the filter 10 has a transmission line 20 and four spaced resonators 12, 14, 16 and 18.
  • the resonators are spaced and extend generally orthogonally from the transmission line 20.
  • the transmission line 20 is terminated to ground.
  • a first resonator 12 is coupled to the input transmission line 22 by interdigitized input coupling means 24.
  • a last resonator 18 is coupled to an output transmission line 26 by interdigitized output coupling means 28.
  • a gold ribbon 30 extends from adjacent the first resonator 12 to adjacent the last resonator 18.
  • the coupling at 32 between the ribbon 30 and the first resonator 12 is capacitive, as indicated by the spacing between the ribbon 30 and the resonator.
  • the coupling at 34 between the ribbon 30 and the last resonator is inductive. This coupling maintains a desired phase differential between the first resonator 12 and the last resonator 18.
  • the ribbon 30 is physically, but not electromagnetically, attached to the substrate at 36 to provide a more secure structure.
  • FIG. 2 The effect on performance resulting from the coupling is indicated in FIG. 2.
  • the typical performance of the uncoupled four-section combline filter 10 is indicated by curve U.
  • the performance of the illustrated coupled four-section combline filter 10 in accordance with the present invention is depicted by curve C.
  • Curve U may be characterized as Chebyshev, whereas the curve U may be characterized as elliptic.
  • the elliptic curve C provides a substantially sharper out-of-band rejection in that its cutoff slopes are much steeper than those of the Chebyshev curve U.
  • the present invention provides an improved filter 10 with little additional bulk, cost or manufacturing complexity.
  • the illustrated device does not require redesigning of the couplings to its environment.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

The present invention provides an improved microwave integrated circuit filter for electromagnetic waves. The filter includes a waveguide and three, four or more resonators spaced from one another and extending from the waveguide. Means, which may include a conductive ribbon, are provided electromagnetically coupling nonadjacent resonators.

Description

BACKGROUND OF THE INVENTION
The present invention relates to filters and, more particularly, to a microwave integrated circuit including a bandpass filter.
In microwave communications, microwave integrated circuit (MIC) filters are used to select utilized frequencies and to reject unwanted frequencies which can result in noise. One design goal of such filters is to obtain sharp out-of-band rejection.
One commonly employed microwave wave circuit (MIC) bandpass filter is the combline filter. This filter includes a longitudinally extending transmission line section and plural, usually four, spaced resonators extending from and orthogonal to the transmission line. The four resonator combline filter represents an useful compromise between economy and effectiveness. More effective filtering can be achieved using more than four resonators, but the added cost and complexity of manufacture tend to outweigh the gain in effectiveness. Furthermore, the added bulk of the larger filters is a significant disadvantage in space and other applications where size and weight are at a premium. What is needed is a compact and economical filter which provides greater filtering effectiveness than the available four-section filter.
SUMMARY OF THE INVENTION
The present invention provides an improved filter for electromagnetic waves. The filter includes a transmission line andl plural resonators spaced from one another and extending from the transmission line. Means are provided electromagnetically coupling nonadjacent resonators.
In a more particular aspect of the present invention, the performance of a standard four-section combline filter in a microwave integrated circuit is enhanced by providing means for coupling the first and fourth resonators. The coupling means may be a gold ribbon, or a ribbon of other conductive material, or an alternative structure. The coupling means may be capacitively coupled to one resonator and inductively coupled to the other. For different applications, both couplings may be inductive, or both may be capacitive.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a bandpass filter in accordance with the present invention.
FIG. 2 is a graph depicting the comparative performances of a coupled filter in accordance with the present invention with an uncoupled filter in accordance with the prior art.
DETAILED DESCRIPTION OF THE INVENTION
A filter 10 in accordance with the present invention includes a multitude of spaced resonators 12, 14, 16 and 18, as shown in FIG. 1. The resonators extend from a common transmission line 20. The comblike structure results in the common appellation "combline" filter. The filter 10 is coupled to an input line 22 by an input coupling means 24 and to an output line 26 by an output coupling means 28. In accordance with the present invention, a conductive ribbon 30 or other means couples nonadjacent resonators 12 and 18.
Describing the illustrated embodiment in greater detail, a microwave integrated circuit 11 includes a substrate 38, preferably of alumina, and a four-section combline filter 10. The filter 10 has a transmission line 20 and four spaced resonators 12, 14, 16 and 18. The resonators are spaced and extend generally orthogonally from the transmission line 20. The transmission line 20 is terminated to ground. A first resonator 12 is coupled to the input transmission line 22 by interdigitized input coupling means 24. A last resonator 18 is coupled to an output transmission line 26 by interdigitized output coupling means 28.
A gold ribbon 30 extends from adjacent the first resonator 12 to adjacent the last resonator 18. The coupling at 32 between the ribbon 30 and the first resonator 12 is capacitive, as indicated by the spacing between the ribbon 30 and the resonator. The coupling at 34 between the ribbon 30 and the last resonator is inductive. This coupling maintains a desired phase differential between the first resonator 12 and the last resonator 18. The ribbon 30 is physically, but not electromagnetically, attached to the substrate at 36 to provide a more secure structure.
The effect on performance resulting from the coupling is indicated in FIG. 2. The typical performance of the uncoupled four-section combline filter 10 is indicated by curve U. The performance of the illustrated coupled four-section combline filter 10 in accordance with the present invention is depicted by curve C. Curve U may be characterized as Chebyshev, whereas the curve U may be characterized as elliptic. The elliptic curve C provides a substantially sharper out-of-band rejection in that its cutoff slopes are much steeper than those of the Chebyshev curve U.
Thus, the present invention provides an improved filter 10 with little additional bulk, cost or manufacturing complexity. The illustrated device does not require redesigning of the couplings to its environment.
Many modifications may be made on the illustrated embodiment within the scope of the present invention. Different materials and resonator arrangements can be considered, including combline filters with more than four elements. The ribbon couplings can be inverted. Furthermore, capacitive or inductive equalization can be achieved, where desired, by making both ribbon couplings capacitive or inductive, respectively. Other response patterns may be achieved by varying the two ribbon couplings.

Claims (4)

What is claimed is:
1. A microwave integrated circuit filter for electromagnetic signals comprising:
a transmission line extending longitudinally;
at least three resonators arranged serially along said transmission line; and
coupling means for electromagnetically coupling two nonadjacent of said resonators, said coupling means comprising a conductive ribbon which is inductively coupled to one of said resonators and is capacitively coupled to another of said resonators.
2. A microwave integrated circuit filter for electromagnetic signals comprising:
a transmission line extending longitudinally;
at least three resonators arranged serially along said transmission line; and
coupling means for electromagnetically coupling two nonadjacent of said resonators, said coupling means comprising a conductive ribbon which is inductively coupled to one of said resonators and is inductively coupled to another of said resonators.
3. A microwave integrated circuit filter for electromagnetic signals comprising:
a transmission line extending longitudinally; p1 first, second, third and fourth resonators arranged serially along said transmission line and extending therefrom, said resonators being spaced from one another; and
coupling means for electromagnetically coupling said first and fourth resonators, said coupling means comprising a conductive ribbon which is inductively coupled to one of said resonators and is capacitively coupled to another of said resonators.
4. A microwave integrated circuit filter for electromagnetic signals comprising:
a transmission line extending longitudinally;
first, second, third and fourth resonators arranged serially along said transmission line and extending therefrom, said resonators being spaced from one another; and
coupling means for electromagnetically coupling said first and fourth resonators, said coupling means comprising a conductive ribbon which is inductively coupled to one of said resonators and is inductively coupled to another of said resonators.
US06/469,498 1983-02-24 1983-02-24 Microwave integrated circuit, bandpass filter Expired - Lifetime US4488130A (en)

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4596969A (en) * 1985-05-08 1986-06-24 Orion Industries, Inc. Interdigital duplexer with notch resonators
US4646038A (en) * 1986-04-07 1987-02-24 Motorola, Inc. Ceramic resonator filter with electromagnetic shielding
US4667172A (en) * 1986-04-07 1987-05-19 Motorola, Inc. Ceramic transmitter combiner with variable electrical length tuning stub and coupling loop interface
US4881050A (en) * 1988-08-04 1989-11-14 Avantek, Inc. Thin-film microwave filter
US4963843A (en) * 1988-10-31 1990-10-16 Motorola, Inc. Stripline filter with combline resonators
US4974260A (en) * 1989-06-02 1990-11-27 Eastman Kodak Company Apparatus for identifying and correcting unrecognizable characters in optical character recognition machines
US5151670A (en) * 1991-04-10 1992-09-29 Radio Frequency Systems, Inc. Duplexing filter
US5317291A (en) * 1992-05-12 1994-05-31 Pacific Monolithics, Inc. Microstrip filter with reduced ground plane
US5506553A (en) * 1993-10-22 1996-04-09 Murata Manufacturing Co., Ltd. High-frequency filter
EP0822655A2 (en) * 1996-07-30 1998-02-04 Trw Inc. Improved low noise block downconverter
US5986525A (en) * 1996-11-08 1999-11-16 Murata Manufacturing Co., Ltd. Filter device having a distributed-constant-line-type resonator
US6359533B1 (en) * 2000-03-07 2002-03-19 Motorola, Inc. Combline filter and method of use thereof
US20030128084A1 (en) * 2002-01-09 2003-07-10 Broadcom Corporation Compact bandpass filter for double conversion tuner
US7742793B2 (en) * 2002-03-08 2010-06-22 Conductus, Inc. Microstrip filter including resonators having ends at different coupling distances
US10056666B2 (en) 2014-05-23 2018-08-21 Tongyu Technology Oy Tuning element for radio frequency resonator

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2749523A (en) * 1951-12-01 1956-06-05 Itt Band pass filters
US3959749A (en) * 1973-10-29 1976-05-25 Matsushita Electric Industrial Co., Ltd. Filter of the distributed constants type
US4418324A (en) * 1981-12-31 1983-11-29 Motorola, Inc. Implementation of a tunable transmission zero on transmission line filters
US4423396A (en) * 1980-09-30 1983-12-27 Matsushita Electric Industrial Company, Limited Bandpass filter for UHF band

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2749523A (en) * 1951-12-01 1956-06-05 Itt Band pass filters
US3959749A (en) * 1973-10-29 1976-05-25 Matsushita Electric Industrial Co., Ltd. Filter of the distributed constants type
US4423396A (en) * 1980-09-30 1983-12-27 Matsushita Electric Industrial Company, Limited Bandpass filter for UHF band
US4418324A (en) * 1981-12-31 1983-11-29 Motorola, Inc. Implementation of a tunable transmission zero on transmission line filters

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4596969A (en) * 1985-05-08 1986-06-24 Orion Industries, Inc. Interdigital duplexer with notch resonators
US4646038A (en) * 1986-04-07 1987-02-24 Motorola, Inc. Ceramic resonator filter with electromagnetic shielding
US4667172A (en) * 1986-04-07 1987-05-19 Motorola, Inc. Ceramic transmitter combiner with variable electrical length tuning stub and coupling loop interface
US4881050A (en) * 1988-08-04 1989-11-14 Avantek, Inc. Thin-film microwave filter
US4963843A (en) * 1988-10-31 1990-10-16 Motorola, Inc. Stripline filter with combline resonators
US4974260A (en) * 1989-06-02 1990-11-27 Eastman Kodak Company Apparatus for identifying and correcting unrecognizable characters in optical character recognition machines
US5151670A (en) * 1991-04-10 1992-09-29 Radio Frequency Systems, Inc. Duplexing filter
US5317291A (en) * 1992-05-12 1994-05-31 Pacific Monolithics, Inc. Microstrip filter with reduced ground plane
US5506553A (en) * 1993-10-22 1996-04-09 Murata Manufacturing Co., Ltd. High-frequency filter
EP0822655A3 (en) * 1996-07-30 1999-01-13 Trw Inc. Improved low noise block downconverter
EP0822655A2 (en) * 1996-07-30 1998-02-04 Trw Inc. Improved low noise block downconverter
US5995818A (en) * 1996-07-30 1999-11-30 Trw Inc. Low noise block downconverter
US5986525A (en) * 1996-11-08 1999-11-16 Murata Manufacturing Co., Ltd. Filter device having a distributed-constant-line-type resonator
US6359533B1 (en) * 2000-03-07 2002-03-19 Motorola, Inc. Combline filter and method of use thereof
US7071798B2 (en) 2002-01-09 2006-07-04 Broadcom Corporation Printed bandpass filter for a double conversion tuner
US20050093661A1 (en) * 2002-01-09 2005-05-05 Broadcom Corporation Printed bandpass filter for a double conversion tuner
US20030128084A1 (en) * 2002-01-09 2003-07-10 Broadcom Corporation Compact bandpass filter for double conversion tuner
US7084720B2 (en) * 2002-01-09 2006-08-01 Broadcom Corporation Printed bandpass filter for a double conversion tuner
US20080036557A1 (en) * 2002-01-09 2008-02-14 Broadcom Corporation Compact bandpass filter for double conversion tuner
US7375604B2 (en) 2002-01-09 2008-05-20 Broadcom Corporation Compact bandpass filter for double conversion tuner
US7567153B2 (en) 2002-01-09 2009-07-28 Broadcom Corporation Compact bandpass filter for double conversion tuner
US7742793B2 (en) * 2002-03-08 2010-06-22 Conductus, Inc. Microstrip filter including resonators having ends at different coupling distances
US10056666B2 (en) 2014-05-23 2018-08-21 Tongyu Technology Oy Tuning element for radio frequency resonator

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